Re: 50W PA Input SWR 3 and up! What can I mess with?
Hi Andy, Ron,
Ron, good point to check the T/R switching, but check all switching diodes: the RX and TX.
My 50W (QCX) PA is also built with the 20m LPF.
I have just tried?quickly driving it with the QMX and the VSWR measured with the QMX was between 1.7:1 to 2.0:1 for 40m to 20m band. The driving RF power was around 4W.
However, when the PA is unkeyed, it means in RX position, than you should have the thru connection to the output so to the dummy load. The VSWR in this case is not 1:1 but it is not unbearable either. This is the R.L. what the receiver feels.
In addition the internal input 3dB attenuator is built as PI attenuator (330 | 22 | 330 Ohm) for 60 Ohm to 60 Ohm, so there are also some parts of a dB of inherent R.L. difference.
--
73 Bojan S53DZ
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Re: 50W PA Input SWR 3 and up! What can I mess with?
likely causes....
D1 bad or backward.
R2/3/4 in the wrong places or wrong values.
or T1 has a shorted turn(s).
I'll toss in soldering problems.
Note: the 10W linear is not even close to the 50w in general design.
--
Allison
------------------
Post online only,?
direct email will go to a bit bucket.
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QCX+ Glitch Sound Power On & Off
I have just completed and tested a QCX+ and I very pleased with it - a big thank you to Hans and the team. The kit is superb and the build was very enjoyable with excellent documentation and on-line resources.
I have just one small question - when I power the QCX+ on and off from the power button I hear a loud glitch sound in my headphones. Is this normal or is there something I can do to overcome it?
Many thanks,
Nick
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Re: 50W PA Input SWR 3 and up! What can I mess with?
Andy, I tested my 20 Meter 50 watt PA using the NanoVNA and found approximately 2:1 all the way out past 50 MHz. I didn't check higher in frequency. When I unkeyed the amp, the SWR went to infinite across the spectrum as expected because the diode switch (D1) opened the RF path to the attenuator. I think it would be beneficial for you to check it both keyed and unkeyed to make sure diode D1 is properly turning on and off. You should not have to add any more attenuation than what is already there. And you should not have to modify the input circuits. This amplifier is usually?a solid performer as designed.? If you are sure the attenuator is properly built and you have checked connections with an ohm meter, and you are sure all the enamel wire is properly installed then you should look closely at the operation of D1.
73 ... Ron
On Wed, Feb 14, 2024 at 12:04 AM, <kontraptioneering@...> wrote:
it looks to me that there's a very happy frequency that this amp wants to operate, which implies that somewhere, this frequency of 10 Mhz is being set by a certain combination of components - capacitors, inductors, etc?
Could it be C2 or C3? And I don't know about changing the number of turns on T1, but maybe? I could experiment with a few things I guess.? Any suggestions for starting points from the crowd? I've attached the schematic for convenience.?
This isn't the first time this has come up here...I'm curious as well.?
I don't know much, but it is interesting to me/ I wonder why 1 uf caps are used on the input here. On the 10W linear PA kit, it goes straight into BS170s for the first stage, and then some 0.1 uf caps before the IRF510s....... And the input transformer is different.? ?
The WA2EBY also uses 0.1 uf on the input.?
-Nate N8BTR
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On Wed, Feb 14, 2024 at 02:30 AM, Donald S Brant Jr wrote:
On Tue, Feb 13, 2024 at 02:43 PM, Adrian YO3GFH wrote:
In my previous post, I've mentioned very fine grained (800 grit) sandpaper used for shining guitar frets, that's the one you should use.
Or one could use the right tool for the job, a contact burnisher:??
I wonder whether the issue will return after cleaning.? A problem might be that too little current is being handled by the contacts, there is a minimum so-called "wetting current" required to break through contact film/oxidation and allow a low-resistance contact:??
Special contact materials and mechanical configurations are used when switching very low currents, to avoid this issue.? Mercury-wetted contacts are an example.
I do not have a schematic handy but I winder if there is a pullup resistor which might be changed to a lower value to put more current through the key contacts.??
73, Don N2VGU
Now I realise I wrote 800 instead of 8000.. I must've been hungry when I posted :-) so it's 8000 grit sandpaper, I just checked. Need to change my glasses :-) That contact burnisher looks nice, but I haven't seen any mention of grit - judging from the picture, looks a bit coarse but, in all fairness, it's not a hi res pic so might be artefacts. I think you make a good point with the minimum current! Regards, YO3GFH op. Adrian
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Re: IQ mode Enabled on version 16
#qmx
Timo - I am on version 16 and could not get IQ to stay on when I was turning it on in the Digi interface menu. However, when I turned it on from within the System config menu it stays on. That might help. Jim Bennett / K7TXA Eagle, ID
toggle quoted message
Show quoted text
On Feb 14, 2024, at 8:03?AM, timo.vandermerwe@... wrote:
?I installed software version 16 on the day it was released.? I use the "IQ mode enable" on HDSDR literally daily and was fine.
Today, for some or other reason, I can set IQ mode to enabled, but as soon as you escape back to the main VFO screen, IQ mode goes back to Disabled.
After several factory resets, going back to version 15, more resets, going back to version 16, some more factory reset, I still can not enable IQ mode.
I moved back to version 14, and all is back to normal.? I can enable IO mode and it sticks.? ? ?
Anyone else seen this.
73 de ZR6TM
Timo?
--
Jim / K7TXA
Eagle, ID
SKCC 10447T
BUG 301
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IQ mode Enabled on version 16
#qmx
I installed software version 16 on the day it was released.? I use the "IQ mode enable" on HDSDR literally daily and was fine.
Today, for some or other reason, I can set IQ mode to enabled, but as soon as you escape back to the main VFO screen, IQ mode goes back to Disabled.
After several factory resets, going back to version 15, more resets, going back to version 16, some more factory reset, I still can not enable IQ mode.
I moved back to version 14, and all is back to normal.? I can enable IO mode and it sticks.? ? ?
Anyone else seen this.
73 de ZR6TM
Timo?
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Re: QMX 20/80m BPF TXswap Clarification
Hans,
Thank you for clarifying the operation of the band swap.
73,?
Steve W6WU?
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Re: 50W PA Input SWR 3 and up! What can I mess with?
On Wed, Feb 14, 2024 at 12:04 AM, <kontraptioneering@...> wrote:
it looks to me that there's a very happy frequency that this amp wants to operate, which implies that somewhere, this frequency of 10 Mhz is being set by a certain combination of components - capacitors, inductors, etc?
Could it be C2 or C3? And I don't know about changing the number of turns on T1, but maybe? I could experiment with a few things I guess.? Any suggestions for starting points from the crowd? I've attached the schematic for convenience.?
This isn't the first time this has come up here...I'm curious as well.?
I don't know much, but it is interesting to me/ I wonder why 1 uf caps are used on the input here. On the 10W linear PA kit, it goes straight into BS170s for the first stage, and then some 0.1 uf caps before the IRF510s....... And the input transformer is different.? ?
The WA2EBY also uses 0.1 uf on the input.?
-Nate N8BTR
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Re: QMX 20/80m BPF TXswap Clarification
Hello Steve? “Regarding the?"20/80m BPF TXswap". Am I correct in assuming that this is in reality is a BPF 1 and BPF 3 swap without regard to which band or slot in the band configuration menu?”.?
My assumption is, yes, however you would know.
No. It swaps a band called "20" with a band called "80". It doesn't swap slots BPF 1 and 3.?
I am quite doubtful that this swap is necessary or beneficial if the proper Rev 2 mod is done? but that needs some testing.? ?
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Re: QMX 20/80m BPF TXswap Clarification
@Hans?
No answers to this question from the group…
“Regarding the?"20/80m BPF TXswap". Am I correct in assuming that this is in reality is a BPF 1 and BPF 3 swap without regard to which band or slot in the band configuration menu?”.?
My assumption is, yes, however you would know.
Thanks,
Steve W6WU?
?
?
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In a private conversation, one of the excellent contributors of this group shared this link, which I wanted to post here for the benefit of others. Its about all the grounding bits included with a passive probe.
https://www.digikey.com/en/blog/why-do-passive-oscilloscope-probes-have-so-many-ground-connection-options
--
regards,
Bryan, N0LUF
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Hi Joan,
just wondering, if this could be the GPS-protection kicking in due to RF on the keying line? Did you notice any "G" in the display?
Maybe deactivate GPS protection, if you anyway don't use one.
72, Willy, oe1wyc+oe3wyc?
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Hi Don. That contact burnisher may be too harsh for paddle contacts, especially very costly paddles with silver or gold plated contacts.? I would also be nervous about sandpaper, even very fine sandpaper. It's more suited to cleaning relay contacts which may be phosphor bronze.? ?A plain piece of paper usually does the job on my paddles.? A piece of paper soaked with a little deoxit works even better.? Follow manufacrurer's recommendation if they provide some.? Reliability of contact closure is also a function of current through the contacts. The paddle input circuitry in the QMX has different circuitry for the dit or dah in order to share the dot input with Mic1.? The dit input has a? 2.2K (R218) to Vdd while the dah input goes directly to the microprocessor and depends on an internal pullup in the processor. This may have a lower current than the dit and if the contacts are dirty, depending on current drawn by the internal pullup, if the current is lower when key contacts are closed, the reliability of closures with dirty contacts may be different between dits and dahs due to current differences.? ?I know I'm splitting hairs here and went down the rabbit hole early in the morning.?
- Steve K1RF
------ Original Message ------
Date 2/13/2024 7:30:30 PM
Subject Re: [QRPLabs] #qmx #firmwaare 1_00_016 release (bug fixes)
On Tue, Feb 13, 2024 at 02:43 PM, Adrian YO3GFH wrote:
In my previous post, I've mentioned very fine grained (800 grit) sandpaper used for shining guitar frets, that's the one you should use.
Or one could use the right tool for the job, a contact burnisher:??
I wonder whether the issue will return after cleaning.? A problem might be that too little current is being handled by the contacts, there is a minimum so-called "wetting current" required to break through contact film/oxidation and allow a low-resistance contact:??
Special contact materials and mechanical configurations are used when switching very low currents, to avoid this issue.? Mercury-wetted contacts are an example.
I do not have a schematic handy but I winder if there is a pullup resistor which might be changed to a lower value to put more current through the key contacts.??
73, Don N2VGU
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Re: QMX Receive suddenly stop working
Howard, Checking the bias voltage to the mux usually provides a good test of 3253 health. It can be measured at a number of easily accessible points, such as any terminal of T401, or on C406. It should be approximately 2.5V relative to ground. Any reading that deviates significantly from that, up or down, is a strong indication of mux failure.
Good luck ! JZ
I am using 20m-80m model of QMX. It is self assembly. It is still transmitting and produce right power level.
Seems like I should check 3253 from you description. However I am not sure how to do so?
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Re: QMX Receive suddenly stop working
I am using 20m-80m model of QMX. It is self assembly. It is still transmitting and produce right power level.
Seems like I should check 3253 from you description. However I am not sure how to do so?
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Thanks Martin, it's very helpful.
Giuseppe iu8eun
is an interesting project, where QRP stations are invited to announce their activity by self spotting themselves in that cluster.
Maybe something the QRP labs comunity can benefit from
DK3UW
Martin
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qrpcluster.com is an interesting project, where QRP stations are invited to announce their activity by self spotting themselves in that cluster.
Maybe something the QRP labs comunity can benefit from
DK3UW
Martin
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good morning everyone, yesterday morning I wanted to do a test with the QMX second high band version with firmware 1_00_015, the first transmission went very well, the time was set perfectly by the qlg1 and it gives me 7 w output, not a single band antenna perfectly tuned to 20 meters with swr 1 or -, the problem is that on the second transmission and all subsequent ones it did not transmit any power, the swr protection was deactivated, have any of you had the same problem or know what it could be, it would be the case update the firmware to 1_00_016?? Thank you and good day.
Giuseppe iu8eun
Hi Philip
I just did a single WSPR transmission on 40m with the GPS plugged in. See attached... Not burning any DX but then again my power supply is at 7.5V (12V QMX) and it's 40m and still daytime; furthermore my antenna wire (long side of the OCFD) fell down and lies on the metal roof. It really doesn't work well, it stops the internet working in my entire house, even at such low power! Anyway no SWR tripping...
On Sat, Feb 10, 2024 at 5:11?PM Hans Summers via <hans.summers= [email protected]> wrote: Stand alone only.
Then that's very strange. I'd wonder in that case if there is some common mode feedline issue (a.k.a. grounding?issue,? a.k.a. in shack), and perhaps adding your GPS connection does something that pushes the SWR over the limit - though SWR and common mode currents aren't the same the causes and symptoms have some relation... to test it, I'd suggest checking with a dummy load.?
If you do still see it on the dummy load then please could you show me exactly what WSPR settings you used and describe it so I can try to reproduce it? Because here everything is running just fine on WSPR with the GPS connected. As a general rule, if there's a software bug, I have?to be able to reproduce it before I can fix it.?
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Re: QMX Receive suddenly stop working
Howard ,
There is some additional info that you can provide to help steer the suggestions in the right direction.
What band model QMX? (HB or LB) are you using? What version level? Was it factory made or did you assemble it? Does it still transmit and produce proper power levels?
There are several possibilities that could result in a deaf RX. Loss of an intermittent solder joint especially at the band switch inductor is one. Failure of the band switch mux chip is also a possibility. Failure of the T/R switch transistor will also deny signal passage, but TX power would likely be affected, too.
JZ KJ4A?
My QMX was working fine and I made couple of QSO via FT8. However I noticed the receiver stop working:
1. I can still hear some strong signals.
2. When I plugin my attena, the S-meter in WSJT-x is not changed. keep in less than 10db. when it was working, it should be around 30-40db.
3. I use rs232 console to test RF filter, it show very large att.
I verified all bands are like this. Compare to operation guide, the Y-axis is significant small (-30db).
Any suggestions what I should check?
-Howard?
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Ronald Taylor
Howard Su